Control of Coagulant Dosing for Humic Substances Based on Ultraviolet Spectrum Analysis

Huan jing ke xue= Huanjing kexue
Bei-Chen ZhangHaiou Huang

Abstract

Humic substance (HS) is a main component of dissolved organic matter in the aquatic environment and significantly affects water treatment processes. To investigate the applicability and principle of UV spectrum analysis for coagulation control, laboratory jar tests were conducted with synthetic waters that had varying concentrations of HS and kaolinite. Thus, the influence of water quality conditions on the optimal coagulant dose (OCD) was determined and further correlated to Specific Ultraviolet Absorbance (SUVA254) and the ultraviolet spectral slopes of the coagulated water. Subsequently, the relationship between the UV spectral slopes and organic fractionation was further identified by using size exclusion chromatography (SEC). The results showed that the coagulant demands of the synthetic waters were positively related to dissolved organic carbon (DOC). Consequently, a stoichiometric relationship (0.61 mg·mg-1 calculated as Al/DOC) was found between the coagulant demand and initial DOC of the synthetic water. As the coagulant dose increased, SUVA254 decreased from 8.9 L·(mg·m)-1 to a steady level of 2.0 L·(mg·m)-1 and the removal efficiency of DOC was positively correlated with SUVA254. Spectral slopes in different waveleng...Continue Reading

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